This invention relates to a method and apparatus for inserting an elongated, bendable drainage mat having a rectangular transverse cross section below the surface of the ground in a vertical orientation. Such drainage mat comprises a polymeric core having a plurality of substantially rigid fingers extending from one side of a layer and an enveloping water-permeable fabric. Such drainage mat is particularly advantageous, for instance as highway edge drain.
The need for drainage systems for highways and other applications has been well known for years, perhaps for several hundred years or more. As the knowledge of the effects of water on the stability of subsurface soil has increased, the design of drainage systems has evolved with new materials of constructions, such as synthetic polymeric engineering fabrics and polymeric conduits and collectors. A major advance in drainage materials is an elongated bendable drainage mat having a rectangular transverse cross section where said drainage mat comprises a polymeric core having a plurality of substantially rigid fingers extending from side of a layer and an enveloping water-permeable fabric. Such drainage mat is disclosed in copending patent applications Ser. No. 481,104, filed Mar. 31, 1983 and application Ser. No. 480,990, filed Mar. 31, 1983, both of which are incorporated herein by reference.
Some drainage material, either because of excess rigidity or difficulty in handling, must be installed, for instance in a highway edge drain application by excavating a considerable length of trench, hauling away the excavated material, inserting the drainage product in the trench and refilling the trench with coarse fill which is substantially pervious to water. Such drainage systems are disadvantageous on the basis of substantial cost to install, for instance in terms of labor for excavation, installation and backfilling as well as costs associated with haulage of excavated and clean backfill material.
Some improvements in installation methods have been achieved by the use of drainage material such as fabric-covered perforated polymeric conduit such as disclosed by Sixt et.al. in U.S. Pat. No. 3,830,373. Installation of such fabric-covered perforated polymeric conduit is facilitated by the use of machine installation apparatus wherein sets of rollers can be utilized to pick up such drainage material lying on the ground and direct the material into the bottom of a trench. Such rollers are conveniently installed in a boot which is advancing in an excavated trench. Such apparatus is readily useful only for multidirectionally flexible drainage material such as flexible polymeric pipe. The elongated bendable drainage mat having a rectangular transverse cross section described above is not multidirectionally bendable but rather is readily bendable only into one of its major surfaces. In this regard the following definitions are useful in describing such drainage mat and the method and apparatus of this invention for installing such drainage mat.
The term "elongated drainage mat" as used in this application refers to a drainage mat having a length substantially larger than its width or depth.
The term "axis of elongation" as used in this application refers to the axis passing through the center of an elongated drainage mat along its length.
The term "transverse rectangular cross section" as used in this application refers to a cross section of an elongated drainage mat in a plane normal to the axis of elongation of the drainage mat.
The term "pointing" as used in this application means a direction in which the axis of elongation of an elongated drainage mat is extended or aimed.
An elongated drainage mat is said to be "vertically-pointed" when the axis of elongation of the drainage mat is generally vertical with respect to the surface of the earth.
An elongated drainage mat is said to be "horizontally-pointed" when the axis of elongation of the drainage mat is generally horizontal with respect to the surface of the earth.
The term "orientation" as used in this application refers to the attitude of an elongated drainage mat having a rectangular transverse cross section determined by the relationship of the axes of the rectangular transverse cross section.
An elongated, horizontally-pointed drainage mat having a rectangular transverse cross section is said to be "vertically-oriented" when the axis of the rectangular transverse cross section having the larger dimension is in a vertical position and similarly, the axis of the rectangular transverse cross section having the smaller dimension is in a horizontal position. The same drainage mat, when rotated 90.degree. around its axis of elongation, is said to be "horizontally-oriented".
This invention overcomes the disadvantanges of methods and apparatus for installing drainage materials such that elongated bendable drainage mat having a rectangular cross section and bendable only into one of its major surfaces can be readily and advantageously installed below the surface of the ground in a vertical orientation in an advancing trench segment.